Hybrid electrochemical cell

ABSTRACT

Disclosed is a hybrid electrochemical cell with a first conductor having at least one portion that is both a first capacitor electrode and a first battery electrode. The hybrid electrochemical cell further includes a second conductor having at least one portion that is a second capacitor electrode and at least one other portion that is a second battery electrode. An electrolyte is in contact with both the first conductor and the second conductor. In some embodiments, the hybrid electrochemical cell further includes a separator between the first conductor and the second conductor to prevent physical contact between the first conductor and the second conductor, while facilitating ion transport between the first conductor and the second conductor.

PRIORITY

This application is a continuation of U.S. patent application Ser. No.17/080,352, filed Oct. 26, 2020, which is a continuation of U.S. patentapplication Ser. No. 16/223,869, filed Dec. 18, 2018, now U.S. Pat. No.10,847,852, which is a divisional of U.S. patent application Ser. No.15/319,286, filed Dec. 15, 2016, now U.S. Pat. No. 10,211,495, which isa 35 USC 371 National Phase filing of International application numberPCT/US15/36082, filed Jun. 16, 2015, which claims the benefit of U.S.provisional patent application No. 62/012,835, filed Jun. 16, 2014, thedisclosures of which are incorporated herein by reference in theirentireties.

GOVERNMENT SUPPORT

This research was supported in part by the Ministry of Higher Educationof Egypt through a graduate research fellowship—the Missions Program.

FIELD OF THE DISCLOSURE

The disclosure relates to electrochemical cells and in particular to ahybrid electrochemical cell having an energy density typical of abattery and a power density typical of a supercapacitor.

BACKGROUND

Batteries are used to power portable electronics such as smartphones,tablets, and laptop computers. Batteries have affected various aspectsof modern living. There are numerous applications for batteries.Moreover, batteries are integral for renewable energy production fromsun and wind as well as the development of electric and hybrid electricvehicles. Batteries store a large amount of charge throughelectrochemical reactions and typically take hours to recharge. What isneeded is a hybrid electro-chemical cell that is quickly rechargeablelike a supercapacitor and that stores a large amount of charge like abattery.

SUMMARY

A hybrid electrochemical cell having a first conductor with at least oneportion that is both a first capacitor electrode and a first batteryelectrode is disclosed. The hybrid electrochemical cell further includesa second conductor having at least one portion that is a secondcapacitor electrode and at least one other portion that is a secondbattery electrode. An electrolyte is in contact with both the firstconductor and the second conductor.

In some embodiments, the hybrid electrochemical cell further includes aseparator between the first conductor and the second conductor toprevent physical contact between the first conductor and the secondconductor, while facilitating ion transport between the first conductorand the second conductor. Moreover, at least one exemplary embodiment ofthe hybrid electrochemical cell relies on lithium-ion (Li-Ion)chemistry. Other exemplary embodiments of the hybrid electrochemicalcell are based upon nickel-cadmium (Ni—Cd) and nickel-metal hydride(Ni-MH) chemistries. Further still, some embodiments of the hybridelectrochemical cell are sized to power electric vehicles fortransportation, while other embodiments are sized small enough to powerimplantable medical devices.

Generally described herein, in certain embodiments, is an energy storagetechnology comprising a supercapacitor designed to store charge on thesurface of large surface area materials. In some applications, thedisclosed supercapacitor captures and releases energy in seconds and cando so through millions of cycles. Further described herein is animprovement that provides greater charge storage capacity using, forexample, power systems that combine supercapacitors and batteries thatprovide for a high charge storage capacity of batteries and the quickrecharge of supercapacitors. Indeed, the inventors have identified, andhave described methods, devices, and systems that solve severallong-felt and unmet needs for devices that include electrochemicalenergy storage having relatively fast energy recharge times in contrastto batteries with relatively slow recharge times that limit mobility ofa user.

In certain aspects, described herein are power systems, methods, anddevices based upon combinations of supercapacitors and batteries forvarious applications, including by way of non-limiting examples electricand hybrid electric vehicles. For example, electric vehicles are oftenpowered by one of the following energy storage systems: fuel cells,batteries, or supercapacitors. However, installing only one type ofconventional energy storage is often insufficient.

In addition, the running cost of the normally available supercapacitorand battery-based power systems is expensive and they are relativelybulky in size. As a result, such power systems are not usable in apractical manner with portable electronics, such as smartphones,tablets, and implantable medical devices.

Advantages of the subject matter described herein are robust andnumerous. For example, one advantage of the subject matter describedherein is a hybrid electrochemical cell that provides the high energydensity of a battery with the high power density of a supercapacitor. Insome embodiments, the hybrid electrochemical cells provided herein donot require an electronic converter and/or bulky packaging. As anotherexample, the subject matter described herein provides a hybridelectrochemical cell that combines a supercapacitor and battery thatdoes not necessarily require wiring a battery to a supercapacitor inparallel, nor does it necessarily require expensive electronicconverters that are required to control power flow between the batteryand supercapacitor.

In one aspect, described herein are methods, devices, and systems thatprovide for a hybrid electrochemical cell with a first conductor havinga single portion that is both a first capacitor electrode and a firstbattery electrode. For example, the hybrid electrochemical cell furtherincludes a second conductor having at least one portion that is a secondcapacitor electrode and at least one other portion that is a secondbattery electrode. In certain applications, an electrolyte is in contactwith both the first conductor and the second conductor.

In some embodiments, the hybrid electrochemical cell further includes aseparator between the first conductor and the second conductor toprevent physical contact between the first conductor and the secondconductor, while still facilitating ion transport between the firstconductor and the second conductor. Moreover, at least one exemplaryembodiment of the hybrid electrochemical cell relies on lithium-ion(Li-Ion) chemistry. Other exemplary embodiments of the hybridelectrochemical cell are based upon nickel-cadmium (Ni—Cd) and/ornickel-metal hydride (Ni-MH) chemistries. Further still, someembodiments of the hybrid electrochemical cell are sized to powerelectric vehicles for transportation, while other embodiments are sizedsmall enough to power implantable medical devices.

In one aspect, provided herein are methods, devices, and systemscomprising a hybrid electrochemical cell comprising: (a) a firstconductor having at least a one portion that is both a first capacitorelectrode and a first battery electrode; (b) a second conductor havingat least one portion that is a second capacitor electrode and at leastone other portion that is a second battery electrode; and (c) anelectrolyte in contact with both the first conductor and the secondconductor. In some embodiments, provided herein is a method, device, andsystem that comprises a hybrid electrochemical cell that contains aseparator between the first conductor and the second conductor that isconfigured in a manner to prevent or reduce physical contact between thefirst conductor and the second conductor and that facilitates iontransport between the first conductor and the second conductor. In someembodiments, the hybrid electrochemical cell comprises lithium-ion(Li-Ion) chemistry. In further or additional embodiments, the firstconductor of the hybrid electrochemical cell is negative and is dopedwith lithium ions. In certain embodiments, the hybrid electrochemicalcell comprises a first conductor that comprises a graphite negativeelectrode. In some embodiments, a first negative battery electrodecomprises: hard carbon, silicon alloy, and/or composite alloy. Incertain embodiments, the second battery electrode comprises a layeredmetal oxide positive electrode, and the second capacitor electrodecomprises an activated carbon positive electrode. In some embodiments,provided is a hybrid electrochemical cell wherein the second positivebattery electrode comprises: lithium cobalt oxide, lithium manganeseoxide, lithium nickel oxide, lithium nickel manganese cobalt oxide,lithium nickel cobalt aluminum oxide, lithium titanium oxide, or lithiumiron phosphate. In certain applications, the second capacitor electrodeand the second battery electrode are delineated. In some embodiments,the second capacitor electrode and the second battery electrode areconnected internally in parallel on one cell, and wherein the capacitorelectrode acts as a buffer to prevent or reduce high rate charge anddischarge of the battery. In some embodiments, the ratio between theportion of the second capacitor electrode and the second batteryelectrode is about 1:1. In some applications, the ratio between theportion of the second capacitor electrode and the second batteryelectrode is within the range of from about 1:10 to about 10:1. In stillfurther or additional embodiments, a desirable power density of thehybrid electrochemical cell is achieved with an increase of a ratiobetween the portion of the second capacitor electrode and the secondbattery electrode. In yet further or additional embodiments, an energydensity of the hybrid electrochemical cell is achieved with a decreaseof the ratio between the portion of the second capacitor electrode andthe second battery electrode. In still further or additionalembodiments, the second capacitor electrode comprises an electric doublelayer capacitor (EDLC) in which charge is stored in the double layers.In some of these additional embodiments, the second capacitor electrodecomprises activated carbon.

In another aspect, described herein are methods, devices, and systemsthat provide for a hybrid electrochemical cell comprising: (a) a firstconductor having at least a one portion that is both a first capacitorelectrode and a first battery electrode; (b) a second conductor havingat least one portion that is a second capacitor electrode and at leastone other portion that is a second battery electrode; and (c) anelectrolyte in contact with both the first conductor and the secondconductor, provided that at least one second capacitor electrodecomprises an electric double layer capacitor (EDLC) in which charge isstored in the double layers. In some of these additional embodiments,the second capacitor electrode comprises an interconnected corrugatedcarbon-based network (ICCN). In certain embodiments, the interconnectedcorrugated carbon-based network (ICCN) electrode comprises a pluralityof expanded and interconnected carbon layers that include a corrugatedcarbon layer. In some embodiments, each expanded and/or interconnectedcarbon layer comprises at least one corrugated carbon sheet that isabout one atom thick. In some embodiments, each expanded andinterconnected carbon layer comprises a plurality of corrugated carbonsheets. In further or additional embodiments, the thickness of the ICCN,as measured from cross-sectional scanning electron microscopy (SEM) andprofilometry, is around about 7 or about 8 μm. In some embodiments, arange of thicknesses of the plurality of expanded and interconnectedcarbon layers making up the ICCN is from around about 5 μm to 100 μm. Infurther or additional embodiments, the second capacitor electrode isredox active to store charge via intercalation pseudo-capacitance. Insome of these embodiments, the second capacitor electrode comprisesniobium pentoxide (Nb₂O₅).

In another aspect, described herein are methods, devices, and systemscomprising a hybrid electrochemical cell comprising: (a) a firstconductor having at least a one portion that is both a first capacitorelectrode and a first battery electrode; (b) a second conductor havingat least one portion that is a second capacitor electrode and at leastone other portion that is a second battery electrode; and (c) anelectrolyte in contact with both the first conductor and the secondconductor, provided that the hybrid electrochemical cell is integratedon a micro-scale. In certain applications, the micro-hybridelectrochemical cell is flexible in size and shape. In some embodiments,the micro-hybrid electrochemical cell is integrated into an implantablemedical device, a smart card, a radio frequency identification (RFID)tag, a wireless sensor, or a wearable electronic. In further oradditional embodiments, the micro-hybrid electrochemical cell isincorporated into a self-powered system. In some applications, themicro-hybrid electrochemical cell is fabricated on the backside of asolar cell of a device. In some embodiments, the second capacitorelectrode and the second battery electrode each has an electrode digitwith a length L, a width W, and an interspace I. In certain embodiments,a length L is about 4000 μm to about 5000 μm, a width is about 300 μm toaround about 1800 μm, and a interspace I is about 100 μm to about 200μm. In further or additional embodiments, a miniaturization of the widthW of the electrode digits and the interspace I between the electrodedigits in the micro-hybrid electrochemical cell reduces ionic diffusionpathways.

In yet another aspect, provided herein are methods, devices, and systemscomprising a hybrid electrochemical cell comprising: (a) a firstconductor having at least a one portion that is both a first capacitorelectrode and a first battery electrode; (b) a second conductor havingat least one portion that is a second capacitor electrode and at leastone other portion that is a second battery electrode; and (c) anelectrolyte in contact with both the first conductor and the secondconductor, provided that the hybrid electrochemical cell relies on orcomprises nickel-cadmium (Ni—Cd) and/or nickel-metal hydride (Ni-MH)chemistries. In certain embodiments, the first conductor is positive andincludes nickel oxyhydroxide (NiOOH) that reduces to nickel hydroxide(Ni(OH)₂) during discharge. In further or additional embodiments, thesecond capacitor electrode and the second battery electrode are positiveelectrodes. In some embodiments, the second capacitor electrode and thesecond battery electrode are delineated. In still further or additionalembodiments, the ratio between the portion of the second capacitorelectrode and the second battery electrode is about 1:1. In someembodiments, the ratio between the portion of the second capacitorelectrode and the second battery electrode is from about 1:10 to about10:1. In some embodiments, a power density of the hybrid electrochemicalcell is achieved with an increase of a ratio between the portion of thesecond capacitor electrode and the second battery electrode. In certainapplications, an energy density of the hybrid electrochemical cell isachieved with a decrease of the ratio between the portion of the secondcapacitor electrode and the second battery electrode. In someapplications, the hybrid electrochemical cell is flexible in size andshape. In some embodiments, the second capacitor electrode and thesecond battery electrode each has an electrode digit with a length L, awidth W, and an interspace I. In certain embodiments, the length L isaround about 4000 μm to about 5000 μm, the width W ranges from aroundabout 300 μm to about 1800 μm, and the interspace I ranges from about100 μm to about 200 μm. In some embodiments, a miniaturization of thewidth W of the electrode digits and the interspace I between theelectrode digits in the micro-hybrid electrochemical cell reduces ionicdiffusion pathways.

In another aspect, provided is a method of manufacturing a hybridelectrochemical cell, the method comprising providing a first conductor,a second conductor and an electrolyte, wherein: (a) the first conductorhas a single portion that is both a first capacitor electrode and afirst battery electrode; (b) the second conductor has at least oneportion that is a second capacitor electrode and at least one otherportion that is a second battery electrode; and (c) the electrolyte isin contact with both the first conductor and the second conductor.

In another aspect, provided is a method of manufacturing a micro-hybridelectrochemical cell comprising lithium-ion (Li-Ion) material, themethod comprising growing porous positive and negative electrodematerials on ICCN interdigitated patterns, wherein the ICCN pattern iscreated using a consumer-grade optical disc burner drive, comprising aseries of steps of: (a) a first step, wherein a graphite oxide (GO)dispersion in water is dropcast onto an optical disc and dried in air toform a graphite film; (b) a second step, wherein a micro-pattern madewith imaging or drafting software is directly printed onto the GO-coatedoptical disc, and wherein the GO film absorbs the energy from a laserand is converted into an ICCN pattern; (c) a third step, wherein anodeand cathode materials are sequentially electrodeposited on the ICCNscaffold, and voltage-controlled and current-controlledelectrodeposition is used to ensure conformal coating of the activematerials throughout the three-dimensional (3D) structure of the ICCN;(d) a fourth step, wherein a nickel-tin alloy, silicon, or graphitemicro-particles are electrodeposited onto ICCN corresponding to theanode; and (e) a fifth step, wherein a drop of electrolyte is added toprovide ions that allow continuous electron flow when the micro-hybridelectrochemical cell is under load.

Another aspect of the subject matter described herein provides for amethod of manufacturing a micro-hybrid electrochemical cell relying onNi—Cd and/or Ni-MH chemistries, the method comprising growing porouspositive and negative electrode materials on ICCN interdigitatedpatterns, wherein the ICCN pattern is created using an optical discburner drive, comprising a series of steps of: (a) a first step, whereina graphite oxide (GO) dispersion in water is dropcast onto an opticaldisc and dried in air to form a graphite film; (b) a second step,wherein a micro-pattern made with imaging or drafting software isdirectly printed onto the GO-coated optical disc, and wherein the GOfilm absorbs the energy from a laser and is converted into an ICCNpattern; (c) a third step, wherein voltage-controlled andcurrent-controlled electrodeposition is used to ensure conformal coatingof the active materials throughout the 3D structure of ICCN, and a metalsuch as lanthanum nickel (LaNi₅) or palladium (Pd) is electrodepositedon ICCN microelectrodes making up the second battery electrode thatforms a portion of an anode; (d) a fourth step, wherein cadmiumhydroxide (Cd(OH)₂) is added to the ICCN corresponding to the anode; and(e) a fifth step, wherein a drop of electrolyte is added to provide ionsthat allow continuous electron flow when the micro-hybridelectrochemical cell is under load.

Those skilled in the art will appreciate the scope of the disclosure andrealize additional aspects thereof after reading the following detaileddescription in association with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings incorporated in and forming a part of thisspecification illustrate several aspects of the disclosure, and togetherwith the description, serve to explain the principles of the disclosure.

FIG. 1 is a diagram of a non-limiting, illustrative depiction of alithium ion (Li-Ion) based hybrid electrochemical cell in accordancewith the present disclosure.

FIG. 2 is a non-limiting, illustrative depiction of a line drawing of asample of an interconnected corrugated carbon-based network (ICCN) thatis usable to make up capacitor electrodes for hybrid electrochemicalcells.

FIG. 3 is a non-limiting, illustrative depiction of a diagram depictinga Li-Ion based micro-hybrid electrochemical cell.

FIG. 4 is a non-limiting, illustrative depiction of a process flowdiagram depicting fabrication of the micro-sized Li-Ion based hybridelectrochemical cell of FIG. 3 .

FIG. 5 is a non-limiting, illustrative depiction of an embodimentsuitable for realizing hybrid electrochemical cells of eithernickel-cadmium (Ni—Cd) and/or nickel-metal hydride (Ni-MH) chemistries.

FIG. 6 is a non-limiting, illustrative depiction of a micro-sized hybridelectrochemical cell based on either Ni—Cd or Ni-MH chemistries.

FIG. 7 is a non-limiting, illustrative depiction of a process flowdiagram illustrating fabrication of the micro-sized hybridelectrochemical cell of FIG. 6 .

FIG. 8A is a charge-discharge graph of voltage versus time for a priorart Li-Ion capacitor.

FIG. 8B is a charge-discharge graph of voltage versus time for a priorart Li-Ion battery.

FIG. 8C is a non-limiting, illustrative depiction of a charge-dischargegraph of an embodiment of a voltage versus time for a hybridelectrochemical cell of the present disclosure.

FIG. 9 is a non-limiting, illustrative depiction of a charge-dischargegraph of voltage versus time for a hybrid electrochemical cell of thepresent disclosure that comprises redox active niobium pentoxide(Nb₂O₅).

FIG. 10A is a graph depicting a charge-discharge curve for a prior artnickel-carbon supercapacitor.

FIG. 10B is a graph depicting a charge-discharge curve for both a priorart Ni—Cd battery and a prior art Ni-MH battery.

FIG. 10C is a non-limiting, illustrative depiction of a charge-dischargegraph of voltage versus time for embodiments of either of the Ni—Cd andthe Ni-MH chemistries comprising hybrid electrochemical cells of thepresent disclosure.

FIG. 11 is a non-limiting, illustrative depiction of a Ragone plotcomparing power density versus energy density for capacitors,supercapacitors, Li-Ion capacitors, batteries, and the hybridelectrochemical cells of the present disclosure.

FIG. 12A is a non-limiting, illustrative depiction of an implantablemedical device having a hybrid electrochemical cell of the presentdisclosure integrated within.

FIG. 12B is a non-limiting, illustrative depiction of a smart cardhaving a hybrid electrochemical cell of the present disclosureintegrated within.

FIG. 12C is a non-limiting, illustrative depiction of a radio frequencyidentification (RFID) tag having a hybrid electrochemical cell of thepresent disclosure integrated within.

FIG. 12D is a non-limiting, illustrative depiction of a wireless sensorhaving a hybrid electrochemical cell of the present disclosureintegrated within.

FIG. 12E is a non-limiting, illustrative depiction of a wearable devicehaving a hybrid electrochemical cell of the present disclosureintegrated within.

FIG. 12F is a non-limiting, illustrative depiction of a solar cellhaving a hybrid electrochemical cell of the present disclosureintegrated with the solar cell to realize an energy harvesting system.

DETAILED DESCRIPTION

Upon reading the following description in light of the accompanyingdrawings, those skilled in the art will understand the concepts of thedisclosure and will recognize applications of these concepts notparticularly addressed herein. It should be understood that theseconcepts and applications are non-limiting and fall within the scope ofthe disclosure and the accompanying claims.

A feature of the subject matter described herein is a hybridelectrochemical cell. In certain embodiments, the hybrid electrochemicalcells described herein comprise nickel-cadmium (Ni—Cd), nickel-metalhydride (Ni-MH) and/or lithium-ion (Li-Ion) batteries. FIG. 1 , forexample, depicts a non-limiting structure of a Li-Ion based hybridelectrochemical cell 10 in accordance with the present disclosure. Thehybrid electrochemical cell 10 includes a first conductor 12 having asingle portion 14 that is both a first capacitor electrode and a firstbattery electrode. In the Li-Ion based chemistry of the hybridelectrochemical cell 10, the first conductor 12 is negative and is dopedwith lithium ions. The hybrid electrochemical cell 10 includes a secondconductor 16 having at least one portion that is a second capacitorelectrode 18 and at least one other portion that is a second batteryelectrode 20. An electrolyte 22 is in contact with both the firstconductor 12 and the second conductor 16. A separator 24 between thefirst conductor 12 and the second conductor 16 prevents physical contactbetween the first conductor 12 and the second conductor 16, whilefacilitating ion transport between the first conductor 12 and the secondconductor 16. The second capacitor electrode 18 and the second batteryelectrode 20 are delineated by a horizontal dashed line 26 in FIG. 1 .As shown, a ratio between the portion of the second capacitor electrode18 and the second battery electrode 20 is about 1:1. However, it is tobe understood that the ratio between the portion of the second capacitorelectrode 18 and the second battery electrode 20 can range from 1:10 to10:1 (inclusive of all ratios in between those endpoints, including butnot limited to, 2:9, 3:8, 4:7, 5:6, 6:5, 7:4, 8:3, and 9:2). As theportion of the second capacitor electrode 18 increases relative to thesecond battery electrode 20, the power density of the hybridelectrochemical cell 10 increases and the energy density decreases.Likewise, as the portion of the second battery electrode 20 increasesrelative to the second capacitor electrode 18, the energy density of thehybrid electrochemical cell 10 increases and the power densitydecreases. The ratio of the second capacitor electrode 18 relative tothe second battery electrode 20 is predetermined for a givenapplication. For example, a larger ratio of the second capacitorelectrode 18 relative to the second battery electrode 20 is desirable tocapture energy quickly in a regenerative braking system, while a smallerratio of the second capacitor electrode 18 relative to the secondbattery electrode 20 might be desirable for energizing a power tool suchas a portable electric drill.

In understanding the hybrid electrochemical cell 10, it is helpful tonote that a typical lithium ion battery comprises a graphite negativeelectrode and a layered metal oxide positive electrode. In contrast, alithium ion capacitor is made of a graphite negative electrode and anactivated carbon positive electrode. Since the negative electrode inboth designs is graphite, these two devices can be integrated into onecell by connecting internally the battery and capacitor positiveelectrodes in parallel. The capacitor electrode would act as a buffer toprevent high rate charge and discharge of the battery. This canpotentially extend the lifetime of the battery portion of the hybridcell by a factor of ten, leading to energy storage systems that maynever need to be replaced for the lifetime of a product being powered bythe hybrid electrochemical cell 10. In addition, given that the positiveelectrodes of the battery and the capacitor have the same operatingvoltage and current collector, it is possible to blend them together inone positive electrode as shown in FIG. 1 . As a result, the hybridelectrochemical cell 10, in certain embodiments, has only two electrodesinstead of the four electrodes used in traditional power systems havingbattery and supercapacitor combinations. The simplified structure anddesign of the present disclosure's hybrid electrochemical cell 10reduces the manufacturing cost and make powering hybrid automobilesenergy efficient. Moreover, the hybrid electrochemical cell 10 combinesbattery technology and supercapacitor technology into a single cellusing one type of electrolyte, thereby eliminating extra currentcollectors, electrolyte, and packaging. This means that the hybridelectrochemical cell 10 provides a higher energy density thantraditional power systems that combine batteries and supercapacitorswith interfacing electronics for power flow control between thebatteries and supercapacitors. The hybrid electrochemical cell 10 isfabricated using commercial electrode materials, collectors, separators,binders, and electrolytes, which allows for fabrication processes thatare readily scalable to industrial levels.

In some embodiments, the first battery electrode material used comprisesgraphite. Other materials are also suitable. For example, in someembodiments, the first battery electrode comprises hard carbon, silicon,composite alloys Sn(M)-based and Sn(O)-based, and combinations thereof.

In certain embodiments, the second battery electrode material comprises:lithium cobalt oxide, lithium manganese oxide, lithium nickel oxide,lithium nickel manganese cobalt oxide, lithium nickel cobalt aluminumoxide, lithium titanium oxide, and/or lithium iron phosphate, andcombinations thereof.

In some embodiments, the second capacitor electrode 18 is made of amaterial that comprises an electric double layer capacitor (EDLC) inwhich charge is stored in double layers. In some embodiments, the secondcapacitor electrode 18 comprises interconnected corrugated carbon-basednetwork (ICCN) 28 or activated carbon. In yet other embodiments, thesecond capacitor electrode 18 is redox active to store charge viaintercalation pseudo-capacitance. In at least one embodiment, the secondcapacitor electrode 18 comprises niobium pentoxide (Nb₂O₅).

In further or additional embodiments, provided is a lithium ion batterythat comprises or consists of two electrodes and electrolyte solutionproviding a conductive medium for lithium ions to move between theelectrodes. In certain applications, both electrodes allow lithium ionsto move in and out of their interiors. In the charge reactions, incertain embodiments of the subject matter described herein, lithium ionsare deintercalated from the positive material and intercalated into thenegative material. Similarly, in some embodiments, the reverse happenson discharge. The intercalation and deintercalation of lithium ions, incertain applications, causes the flow of electrons in an externalcircuit (not shown).

Another advantage of the subject matter described herein are methods,devices, and systems that provide for the increased movement of ions,including for example, lithium ions, into and out of the electrodes. Aproblem with pure lithium ion batteries is the slow movement of lithiumions in and out of the battery electrodes. As described herein, in someapplications, the insertion of a supercapacitor electrode in the lithiumion-based hybrid electrochemical cell 10 speeds up the charge-dischargeprocess by storing charge via adsorption of ions on the surface of acarbon electrode or through fast redox reactions near the surface of anoxide electrode instead of the bulk of a layered battery material. Forexample, in a carbon supercapacitor electrode, the charge is stored inan electric double at the interface between the carbon and electrolyte.Here, and in these applications of the methods, devices, and systemsdescribed herein, an interface between the electrodes and electrolyte isthought of as an electrical double layer composed of the electricalcharge at the surface of the carbon electrode itself and the charge ofthe ions disbursed in the solution at a small distance from theelectrode surface. This electrical double layer is formed when apotential is applied to the electrode and causes a charging current(non-faradaic current) to pass through the hybrid electrochemical cell10. These reactions are described below.

The following equations describe the charge storage mechanism of certainembodiments of the hybrid electrochemical cell 10, for example, whenusing graphite as the first battery electrode and lithiated metal oxideas the second battery electrodes and carbon as the second capacitorelectrode. At the positive electrode charge storage occurs through acombination of double layer adsorption capacitance and lithium ioninsertion.

$\begin{matrix}{{{LiMO}_{2}\underset{discharge}{\overset{charge}{\rightleftarrows}}{Li}_{1 - x}{MO}_{2}} + {x{Li}}^{+} + {xe^{-}}} \\{{C + {xe}^{+} + {xA^{-}}}\underset{discharge}{\overset{charge}{\rightleftarrows}}{C\left( {e^{+}{❘A_{ads}^{-}}} \right)}}\end{matrix}$

In this scheme, LiMO₂ represents a metal oxide positive material, suchas LiCoO₂, x is a fraction 0<x<1. C is a high surface area form ofcarbon, e⁺ is a hole, and A⁻ is an electrolyte anion, and (e⁺|A_(ads) ⁻)refers to an electric double layer (EDL) formed at the interface betweenthe carbon electrode and electrolyte. At the negative electrode, lithiumion insertion into and out of graphite is described by the followingequation.

${{x{Li}^{+}} + {xe^{-}} + {xC}_{6}}\underset{discharge}{\overset{charge}{\rightleftarrows}}{x{LiC}}_{6}$

FIG. 2 is a non-limiting illustration of a line drawing of a sample ofan interconnected corrugated carbon-based network (ICCN) 28, which ismade up of a plurality of expanded and interconnected carbon layers thatinclude corrugated carbon layers such as a single corrugated carbonsheet 30. In one embodiment, each of the expanded and interconnectedcarbon layers comprises at least one corrugated carbon sheet that is oneatom thick. In another embodiment, each of the expanded andinterconnected carbon layers comprises a plurality of corrugated carbonsheets 30. In this specific example, the thickness of the ICCN 28, asmeasured from cross-sectional scanning electron microscopy (SEM) andprofilometry, was found to be around about 7.6 μm. In one embodiment, arange of thicknesses of the plurality of expanded and interconnectedcarbon layers making up the ICCN 28 is from around about 1 μm to about100 μm. In some embodiments, the thickness of the plurality of expandedand interconnected carbon layers making up the ICCN 28 is from aroundabout 2 μm to about 90 μm, from about 3 μm to about 80 μm, from about 4μm to about 70 μm, from 5 μm to about 60 μm, from about 5 μm to about 50μm, 5 μm to about 40 μm, 5 μm to about 30 μm, 5 μm to about 20 μm, 5 μmto about 10 μm, from about 5 μm to about 9 μm, or from about 6 μm toabout 8 μm.

In some embodiments, hybrid electrochemical cells in accordance with thepresent disclosure are also made on a micro-scale which will enable arelatively large number of applications for a new generation ofelectronics. For example, a micro-hybrid electrochemical cell, in someembodiments, are integrated into implantable medical devices, smartcards, radio frequency identification (RFID) tags, wireless sensors, andeven wearable electronics. Integrated micro-hybrid electrochemicalcells, in some applications, also serve as a way to better extractenergy from solar, mechanical, and thermal sources and thus make moreefficient self-powered systems. Micro-hybrid electrochemical cells, incertain embodiments, are also fabricated on the backside of solar cellsin both portable devices and rooftop installations to store powergenerated during the day for use after sundown, helping to provideelectricity around the clock when connection to the grid is notpossible. Each of these applications is made possible by the subjectmatter described herein based in part on the flexibility in size andshape of the micro-hybrid electrochemical cells described herein.Moreover, in further or additional embodiments, provided is a thin formfactor for the battery that allows for thinner portable electronics.

FIG. 3 is a non-limiting diagram illustrating a lithium ion-basedmicro-hybrid electrochemical cell 32. The micro-hybrid electrochemicalcell 32 includes a first conductor 34 having a single portion 36 that isboth a first capacitor electrode and a first battery electrode. In thelithium ion-based chemistry of the micro-hybrid electrochemical cell 32,the first conductor 34 is negative and is doped with lithium ions. Themicro-hybrid electrochemical cell 32 includes a second conductor 38having at least one portion that is a second capacitor electrode 40 andat least one other portion that is a second battery electrode 42. Anelectrolyte 44 is in contact with both the first conductor 34 and thesecond conductor 38. The second capacitor electrode 40 and the secondbattery electrode 42 each have electrode digits with a length L, a widthW, and an interspace I. In an exemplary millimeter scale embodiment, thelength L is around about 4800 μm, the width W ranges from around about330 μm to around about 1770 μm, and the interspace I is typically aroundabout 150 μm. While these dimensions are exemplary, it is to beunderstood that a further miniaturization of the width W of theelectrode digits and the interspace I between the electrode digits inthe micro-hybrid electrochemical cell 32 would reduce ionic diffusionpathways, thus leading to the micro-hybrid electrochemical cell 32having even higher power density. In an exemplary centimeter scaleembodiment, the length L is around about 1.2 cm, the width W ranges fromaround about 0.05 cm to around about 0.2 cm, and the interspace I istypically around about 0.05 cm.

In some embodiments, the micro-hybrid electrochemical cell 32 isintegrated by growing porous positive and negative electrode materialson ICCN interdigitated patterns. In general, methods for producing themicro-hybrid electrochemical cell 32 having electrodes made of apatterned ICCN typically include an initial step of receiving asubstrate having a carbon-based oxide film. Once the substrate isreceived, a next step involves generating a light beam having a powerdensity sufficient to reduce portions of the carbon-based oxide film toan ICCN. Another step involves directing the light beam across thecarbon-based oxide film in a predetermined pattern via a computerizedcontrol system while adjusting the power density of the light beam viathe computerized control system according to predetermined power densitydata associated with the predetermined pattern. Exemplary light sourcesfor generating the light beam include but are not limited to a 780 nmlaser, a green laser, and a flash lamp. The light beam emission of thelight sources may range from near infrared to ultraviolet wavelengths.

An exemplary process for fabricating the micro-hybrid electrochemicalcell 32 is schematically illustrated in FIG. 4 . In some embodiments,the ICCN pattern is created using a consumer-grade digital versatiledisc (DVD) burner drive. In a first step, a graphite oxide (GO)dispersion in water is dropcast onto a DVD disc and dried in air to forma graphite oxide film 46 (step 100). A micro-pattern made with imagingor drafting software is directly printed onto the GO-coated DVD disc 48(step 102). The GO film absorbs the energy from a laser 50 and isconverted into an ICCN pattern. With the precision of the laser 50, theDVD burner drive renders the computer-designed pattern onto the GO filmto produce the desired ICCN circuits. In certain applications, the ICCNpattern is designed to have three terminals: an ICCN supercapacitor-likeelectrode and two battery electrodes. In some embodiments, the capacityof the supercapacitor electrode is boosted by the electrophoreticdeposition of activated carbon micro-particles.

In further or additional embodiments, anode and/or cathode materials aresequentially electrodeposited on the ICCN scaffold. Voltage-controlledand current-controlled electrodeposition is used to ensure conformalcoating of the active materials throughout the three-dimensional (3D)structure of the ICCN. For example, manganese dioxide (MnO₂) iselectrodeposited on the ICCN microelectrodes making up the secondbattery electrode 42 (FIG. 3 ) that forms a portion of a cathode and isfollowed by a lithiation of MnO₂ in molten lithium nitrate (LiNO₃) andlithium hydroxide (LiOH) (step 104). In some embodiments, polyaniline isused as an alternative to the cathode material. Next, a nickel-tinalloy, silicon, or even graphite micro-particles are electrodepositedonto ICCN corresponding to the anode (step 106). To complete themicro-hybrid electrochemical cell 32, a drop of electrolyte 52 is addedto provide ions that allow continuous electron flow when themicro-hybrid electrochemical cell 32 is under load (step 108).

In some embodiments, the micro-hybrid electrochemical cell 32 isrealized using nickel-cadmium (Ni—Cd) and nickel-metal hydride (Ni-MH)chemistries in a similar manner to that of the lithium ion-based hybridelectrochemical cell 10 (see FIG. 1 ) except that the chemistry of Ni—Cdor Ni-MH batteries is combined with a Ni-carbon asymmetricsupercapacitor.

FIG. 5 depicts a non-limiting structure for a hybrid electrochemicalcell 54 for Ni—Cd and Ni-MH chemistries in accordance with the presentdisclosure. In some embodiments, the hybrid electrochemical battery cell54 includes a first conductor 56 having a single portion 58 that is botha first capacitor electrode and a first battery electrode. In someembodiments, in either of the Ni—Cd and/or Ni-MH based chemistries ofthe hybrid electrochemical cell 54, the first conductor 56 is positiveand includes nickel oxyhydroxide (NiOOH) that reduces to nickelhydroxide (Ni(OH)₂) during discharge. In some embodiments, the hybridelectrochemical cell 54 includes a second conductor 60 having at leastone portion that is a second capacitor electrode 62 and at least oneother portion that is a second battery electrode 64. In someembodiments, the ions that collect on the second battery electrode 64comprise a metal hydride represented by X in the metal hydride case orCd(OH)₂ represented by Y in the Ni—Cd case. In certain applications, anelectrolyte 66 is in contact with both the first conductor 56 and thesecond conductor 60, whereby a separator 68 between the first conductor56 and the second conductor 60 prevents physical contact between thefirst conductor 56 and the second conductor 60, while facilitating iontransport between the first conductor 56 and the second conductor 60. Insome embodiments, the second capacitor electrode 62 and the secondbattery electrode 64 are delineated by a horizontal dashed line 69 inFIG. 5 . As shown, a ratio between the portion of the second capacitorelectrode 62 and the second battery electrode 64 is 1:1. However, it isto be understood that the ratio between the portion of the secondcapacitor electrode 62 and the second battery electrode 64 can rangefrom 1:10 to 10:1 (inclusive of all ratios in between those endpoints,including but not limited to, 2:9, 3:8, 4:7, 5:6, 6:5, 7:4, 8:3, and9:2).

In some embodiments, as the portion of the second capacitor electrode 62increases relative to the second battery electrode 64, the power densityof the hybrid electrochemical cell 54 increases and the energy densitydecreases. Likewise, in further or additional embodiments, as theportion of the second battery electrode 64 increases relative to thesecond capacitor electrode 62, the energy density of the hybridelectrochemical cell 54 increases and the power density decreases. Incertain applications, the ratio of the second capacitor electrode 62relative to the second battery electrode 64 is predetermined for a givenapplication. For example, a larger ratio of the second capacitorelectrode 62 relative to the second battery electrode 64 is desirable tocapture energy quickly in a regenerative braking system, while a smallerratio of the second capacitor electrode 62 relative to the secondbattery electrode 64 might be desirable for energizing a power tool suchas a portable electric drill.

In certain applications this design uses a negative electrode made ofactivated carbon in which the charge is stored in the electric doublelayer, while the positive electrode is pseudocapacitive (typicallyNiOOH) where the charge is stored through redox reactions in the bulk ofthe material. An aqueous alkaline solution is used as an electrolyte inthe same way as in Ni—Cd and Ni-MH batteries. Because the positiveelectrode in Ni—Cd and Ni-MH batteries is NiOOH, the same as intraditional Ni—Cd asymmetric supercapacitors, in certain embodiments,provided is an integration of both devices into one cell by connectingthe battery and capacitor negative electrodes in parallel. In further oradditional embodiments, also provided is a blend of the battery andcapacitor negative electrodes into one electrode.

FIG. 6 is a non-limiting diagram depicting a micro-hybridelectrochemical cell 70 based on either Ni—Cd or Ni-MH chemistries. Insome embodiments, the micro-hybrid electrochemical battery cell 70includes a first conductor 72 having a single portion 74 that is both afirst capacitor electrode and a first battery electrode. In further oradditional embodiments, during fabrication of the micro-hybridelectrochemical cell 70, the first conductor 56 is positive and is dopedwith NiOOH for use with either Ni—Cd or Ni-MH chemistries. In someembodiments, the micro-hybrid electrochemical cell 70 includes a secondconductor 76 having at least one portion that is a second capacitorelectrode 78 and at least one other portion that is a second batteryelectrode 80. In some embodiments, an electrolyte 82 is in contact withboth the first conductor 72 and the second conductor 76. For example,the second capacitor electrode 78 and the second battery electrode 80each have electrode digits with a length L, a width W, and an interspaceI. In an exemplary embodiment the length L is around about 4800 μm, thewidth W ranges from around about 330 μm to around about 1770 μm, and theinterspace I is typically around about 150 μm. While these dimensionsare exemplary, it is to be understood that a further miniaturization ofthe width W of the electrode digits and the interspace I between theelectrode digits in the micro-hybrid electrochemical cell 70 wouldreduce ionic diffusion pathways, thus leading to the micro-hybridelectrochemical cell 70 having even higher power density.

Similar to the fabrication of the Li-Ion based micro-hybridelectrochemical cell 32, the micro-hybrid electrochemical cell 70, basedon either Ni—Cd or Ni-MH chemistries, in certain embodiments isintegrated by growing porous positive and negative electrode materialson ICCN interdigitated patterns. An exemplary process for fabricatingthe micro-hybrid electrochemical cell 70 is schematically illustrated inFIG. 7 . Steps 100 and 102 are completed the same as shown in FIG. 4 .However, new steps are added after step 102 to accommodate the Ni—Cd orNi-MH chemistries to sequentially electrodeposit anode and cathodematerials on the ICCN scaffold. As with the fabrication of Li-Ion basedmicro-hybrid electrochemical cell 32, voltage-controlled andcurrent-controlled electrodeposition is used to ensure conformal coatingof the active materials throughout the 3D structure of ICCN. A metalsuch as lanthanum nickel (LaNi₅) or palladium (Pd) is electrodepositedon ICCN microelectrodes making up the second battery electrode 80 thatforms a portion of an anode (step 110). Next, Cd(OH)₂ is added to theICCN corresponding to the anode (step 112). To complete the micro-hybridelectrochemical cell 70, a drop of electrolyte 82 is added to provideions that allow continuous electron flow when the micro-hybridelectrochemical cell 70 is under load (step 114).

The electrochemical reactions of the Ni-MH and Ni—Cd based hybridelectrochemical cells are described in the following: Ni-MH Based HybridElectrochemical Cell

$\begin{matrix}{{The}{negative}{electrode}} \\{{{- M} + {H_{2}O} + e^{-}}\underset{discharge}{\overset{charge}{\rightleftarrows}}{{OH}^{-} + {MH}}} \\{{{- C} + {xe}^{-} + {xA}^{+}}\underset{discharge}{\overset{charge}{\rightleftarrows}}{C\left( {e^{-}{❘A_{ads}^{+}}} \right)}} \\{{On}{the}{positive}{electrode}} \\{{{- {{Ni}({OH})}_{2}} + {OH}^{-}}\underset{discharge}{\overset{charge}{\rightleftarrows}}{{{NiO}({OH})} + {H_{2}O} + e^{-}}}\end{matrix}$

The metal, M, in the negative electrode of a Ni-MH cell, is actually ahydrogen storage alloy. It comes from a new group of intermetalliccompounds which can reversibly store hydrogen. Many different compoundshave been developed for this application, but the most extensivelyadopted is rare earth-based AB₅-type alloys. In this type of alloy, theA component consists of one or more rare earth elements, and B is mainlycomposed of transition metals such as Ni, Co, Mn, and Al. The capacitorelectrode stores charge in an electric double layer. (e⁻|A_(ads) ⁺)refers to an electric double layer (EDL) formed at the interface betweenthe carbon electrode and electrolyte, where e⁻ is an electron from theelectrode side and A_(ads) ⁺ is a cation from the electrolyte side. Inthe Ni-MH hybrid electrochemical cell, nickel oxyhydroxide (NiOOH), isthe active material in the charged positive electrode. During discharge,it reduces to the lower valence state, nickel hydroxide, Ni(OH)₂, byaccepting electrons from the external circuit. These reactions reverseduring charging of the cell.

Ni—Cd Based Hybrid Electrochemical Cell

$\begin{matrix}{{The}{negative}{electrode}} \\{{{- {{Cd}({OH})}_{2}} + {2e^{-}}}\underset{discharge}{\overset{charge}{\rightleftarrows}}{{Cd} + {2{OH}^{-}}}} \\{{{- C} + {xe}^{-} + {xA}^{+}}\underset{discharge}{\overset{charge}{\rightleftarrows}}{C\left( {e^{-}{❘A_{ads}^{+}}} \right)}} \\{{On}{the}{positive}{electrode}} \\{{{- {{Ni}({OH})}_{2}} + {OH}^{-}}\underset{discharge}{\overset{charge}{\rightleftarrows}}{{{NiO}({OH})} + {H_{2}O} + e^{-}}}\end{matrix}$

In the Ni—Cd based hybrid electrochemical cell, the negative electrodeconsists of cadmium metal and high surface area carbons. During charge,Ni(OH)₂ is oxidized to the higher valence state and releases electronsto the external circuit. These electrons are stored in the negativeelectrode by reducing Cd(OH)₂ to elemental cadmium and in electricdouble layers.

FIG. 8A is a charge-discharge graph of voltage versus time for a priorart lithium ion capacitor. The charge rate and the discharge rate arerelatively steep in comparison to a lithium ion battery charge rate anddischarge rate shown in FIG. 8B. FIG. 8C is a non-limitingcharge-discharge graph of voltage versus time for a hybridelectrochemical cell of the present disclosure. Notice that in thiscase, and in certain embodiments of the present disclosure, the hybridelectrochemical cell has charge rates and discharge rates that arecommensurate with both the lithium ion capacitor and the lithium ionbattery. As a result, the hybrid electrochemical cells of thisdisclosure share the best properties of both the lithium ion capacitorand the lithium ion battery and therefore can be thought of as being“super-batteries.”

The shape of the charge-discharge graph of the hybrid electrochemicalcell is controlled by the type of the second capacitor electrode. Forexample, FIG. 8C describes the case when using a double layer capacitorelectrode such as ICCN 28 or activated carbon. However, when using redoxactive Nb₂O₅, the behavior is illustrated in FIG. 9 . Other materialsare also suitable.

FIG. 10A is a graph depicting a charge-discharge curve for a prior artnickel-carbon supercapacitor. In contrast, FIG. 10B is a graph depictinga charge-discharge curve for both a prior art Ni—Cd battery and a priorart Ni-MH battery. FIG. 10C is a non-limiting illustration of acharge-discharge graph of voltage versus time for either of the Ni—Cdand the Ni-MH chemistries for embodiments comprising hybridelectrochemical cells of the present disclosure. In essence, thecharge-discharge graph of FIG. 10C can be thought of as the result of acombination of the electrochemical properties of nickel-carbonsupercapacitor and Ni—Cd or Ni-MH battery.

A Ragone plot is useful to highlight the improved electrochemicalstorage ability of the hybrid electrochemical cells of the presentdisclosure. FIG. 11 is a Ragone plot comparing the performance of hybridelectrochemical cells with different energy storage devices designed forhigh-power demanding loads. The Ragone plot shows the gravimetric energydensity and power density of the packaged cells for all the devicestested. The Ragone plot reveals a significant increase in performancefor energy density in comparison to traditional supercapacitors.Remarkably, compared with lithium ion supercapacitors, hybridelectrochemical cells of certain embodiments of the subject matterdescribed herein store up to ten times more energy and around about thesame to slightly greater power density than lithium ion supercapacitors.For example, the hybrid electrochemical cells of the present disclosurehave an energy density that ranges between 20 watt-hour/kilogram (Wh/kg)to around about 200 Wh/kg. Furthermore, although lithium ion batteriescan provide high energy density, they have limited power performancethat is nearly two orders of magnitude lower than the hybridelectrochemical cells of the present disclosure. For example, the hybridelectrochemical cells of the present disclosure have a power densitythat ranges between nearly 10³ watt/kilogram (W/kg) to about 10⁴ W/kg.This superior energy and power performance of the hybrid electrochemicalhybrids will compete, completely replace, and/or complement batteriesand supercapacitors, including lithium ion supercapacitors in a varietyof applications. Moreover, a further miniaturization of the width of themicro-electrodes and the space between micro-electrodes in micro-hybridelectrochemical cells would reduce ionic diffusion pathways, thusleading to micro-hybrid electrochemical cells with even higher powerdensity.

Applications for the disclosed embodiments of a micro-hybridelectrochemical cell are diverse. The following list is only exemplary.For example, FIG. 12A is a non-limiting, illustrative depiction of animplantable medical device 84 having the micro-hybrid electrochemicalcell 70 integrated within. FIG. 12B is a non-limiting, illustrativedepiction of a smart card 86 having the micro-hybrid electrochemicalcell 70 integrated within. FIG. 12C is a non-limiting, illustrativedepiction of a radio frequency identification (RFID) tag 88 having themicro-hybrid electrochemical cell 70 of the present disclosureintegrated within. FIG. 12D is a non-limiting, illustrative depiction ofa wireless sensor 90 having the micro-hybrid electrochemical cell 70 ofthe present disclosure integrated within. FIG. 12E is a non-limiting,illustrative depiction of the wearable device 92 having a micro-hybridelectrochemical cell 70 of the present disclosure integrated within.FIG. 12F is a non-limiting, illustrative depiction of a solar cell 94having the micro-hybrid electrochemical cell 70 of the presentdisclosure integrated with the solar cell 94 to realize a self-poweredsystem. Other self-powered systems that will benefit from integrationwith the present embodiments include but are not limited to vibrationaltype energy harvesting systems, wind energy harvesting systems, andtemperature differential type energy harvesting systems.

Those skilled in the art will recognize improvements and modificationsto the embodiments of the present disclosure. All such improvements andmodifications are considered within the scope of the concepts disclosedherein and the claims that follow.

What is claimed is:
 1. An electrode comprising: a. at least one portionthat is a battery electrode; b. at least one portion that is a capacitorelectrode; c. a ratio between the capacitor electrode and the batteryelectrode that is from about 1:10 to about 10:1; and d. graphene formedin an intercorrugated carbon-based network (ICCN).
 2. The electrode ofclaim 1, wherein the electrode comprises an active material deposited onthe electrode.
 3. The electrode of claim 2, wherein the ICCN comprisesthe active material in a conformal coating throughout athree-dimensional (3D) structure of the ICCN.
 4. The electrode of claim3, wherein the active material comprises metal oxide particles.
 5. Theelectrode of claim 4, wherein the metal oxide particles comprise niobiumpentoxide (Nb₂O₅), lanthanum nickel (LaNi₅), cadmium hydroxide(Cd(OH)₂), or palladium (Pd).
 6. The electrode of claim 1, wherein thecapacitor electrode comprises activated carbon.
 7. The electrode ofclaim 3, wherein the capacitor electrode comprises ICCN.
 8. Theelectrode of claim 3, wherein a thickness of the ICCN as measured fromcross-sectional scanning electron microscopy (SEM) and profilometryranges from about 5 μm to about 100 μm.
 9. The electrode of claim 1,wherein the ratio between the capacitor electrode and the batteryelectrode is 1:1.
 10. The electrode of claim 1, wherein the ratiobetween the capacitor electrode and the battery electrode is 2:9, 3:8,4:7, or 5:6.
 11. The electrode of claim 1, wherein the ratio between thecapacitor electrode and the battery electrode is 6:5, 7:4, 8:3, or 9:2.12. The electrode of claim 1, wherein the electrode is configured tofunction in an electrochemical cell comprising Ni—Cd or Ni-MH chemistry.13. The electrode of claim 1, wherein the electrode is configured tofunction in an electrochemical cell comprising lithium ion chemistry.14. The electrode of claim 1, wherein the electrode is a microelectrode.15. The electrode of claim 2, wherein the electrode stores charge viaadsorption of ions on a surface the electrode.